Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 16, 2012 at 06:40 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update March 2, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update March 2, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update March 2, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update March 1, 2012)]

[POES auroral activity level since October 2009 - updated March 5, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Data source change from March 16: The source for planetary A and K indices has been changed from SWPC to WDC (Potsdam) to improve data quality. The change has been applied to old data in the above plot and will gradually be phased in where those data are otherwise used in STAR.

Recent activity

The geomagnetic field was quiet to severe storm on March 15. Solar wind speed at SOHO ranged between 444 and 760 km/s. A fairly strong solar wind shock was observed at SOHO at 12:42 UTC, the arrival of the CME observed on March 13. Solar wind speed had been on the increase since 08h UTC as a high speed stream from CH507 was becoming the dominant solar wind source.

Solar flux measured at 20h UTC on 2.8 GHz was 110.6 (increasing 6.9 over the last solar rotation). The planetary A index was 44 (STAR Ap - based on the mean of three hour interval ap indices: 44.5). Three hour interval K indices: 43335756 (planetary), 33334644 (Boulder).

The background x-ray flux is at the class B3 level.

At midnight UTC the visible solar disk had 9 spotted active regions (in 2K resolution SDO images).

Region 11429 [N18W85] rotated mostly out of view at the northwest limb with only the easternmost spot visible at the end of the day.
Region 11432 [N15W14] decayed slowly losing all rudimentary penumbra.
Region 11433 [N13E11] was quiet and stable.
Region 11434 [S22W01] decayed slowly and quietly.
New region 11435 [S25W11] emerged in the southeast quadrant on March 11 and was noticed by SWPC 4 days later.

Spotted regions not reported by NOAA/SWPC:
[S1525] was split off from region 11432 on March 13. Location at midnight: N13E04. Flare: M1.8/1F at 07:52 UTC at the inversion line between this and AR 11432. A weak type II radio burst was associated with the event. A small and apparently Earth directed CME was observed in STEREO imagery. It is very unusual for regions without mature penumbra to produce M class events, in this case it's interaction between opposite polarity fields in two nearby regions causing the events.
[S1526] emerged near the trailing spot of region 11434 on March 14. Location at midnight: S24E10
[S1528] rotated into view at the southeast limb on March 15. Location at midnight: S13E79
[S1529] emerged in the northeast quadrant on March 15. Location at midnight: N16E42

Coronal mass ejections (CMEs)

March 15: A small CME was observed in STEREO imagery. This CME could reach Earth on March 18.
March 14
: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
March 13: The M7 event in region 11429 was associated with a halo CME which reached Earth on March 15.

Coronal holes

Coronal hole history (since October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A large recurrent trans equatorial coronal hole (CH507) was in an Earth facing position on March 13-14.

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.


Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is very poor. Propagation on long distance northeast-southwest paths is fair to good.


The geomagnetic field is expected to be unsettled to minor storm on March 16 due to a CME and a high speed stream from CH507, quiet to unsettled is likely on March 17-18.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.

Active solar regions

Click on image for higher resolution image) Compare to the previous day's image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) is positive.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.

Active region Date numbered
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlay
2K 1K
11429 2012.03.02
3 1   N19W85 0090 DSO HRX rotated partly out of view
11432 2012.03.08
16 15 8 N14W13 0100 ESI BXI location: N15W14

area: 0010

SWPC includes region S1525
inversion line added in image

S1517 2012.03.09       S25W59           plage
S1520 2012.03.09       N27W56           plage
11434 2012.03.10
2 5 2 S21W01 0030 CAO CRO  
11433 2012.03.10
11 20 10 N12E09 0120 CSI CSO location: N13E11
11435 2012.03.11
3 7 4 S25W11 0030 CRO CRO  
S1525 2012.03.13   9 8 N13W11 0050   DRI inversion line added in images
S1526 2012.03.14   1   S24E10 0000   AXX  
S1527 2012.03.14       N10W29         plage
S1528 2012.03.15   2 1 S13E79 0010   CRO    
S1529 2012.03.15   1   N16E42 0000   AXX    
Total spot count: 35 61 33  
Sunspot number: 85 151 93  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 63 81 53  (Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 51 53 51 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) for STAR SDO 2K, k = 0.55 for STAR SDO 1K

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
2010.12 84.2 14.4 28.8 (+2.3) 4.35
2011.01 83.6 19.1 31.0 (+2.2) 5.51
2011.02 94.6 29.4 33.4 (+2.4)  6.44
2011.03 115.0 56.2 36.9 (+3.5) 8.18
2011.04 112.6 54.4 41.8 (+4.9) 8.83
2011.05 95.8 41.6 47.6 (+5.8) 8.94
2011.06 95.8 37.0 53.2 (+5.6) 8.06
2011.07 94.2 43.9 57.2 (+4.0) 8.16
2011.08 101.7 50.6 59.0 (+1.8) 7.26
2011.09 133.8 78.0 (59.2 projected, +0.2) 12.27
2011.10 137.3 88.0 (59.4 projected, +0.2) 8.28
2011.11 153.5 96.7 (60.8 projected, +1.4) 5.55
2011.12 141.3 73.0 (63.6 projected, +2.8) 3.78
2012.01 132.5 58.3 (67.1 projected, +3.5) 7.15
2012.02 106.5 33.1 (71.0 projected, +3.9) 8.81
2012.03 126.1 (1) 38.4 (2A) / 79.3 (2B) (73.2 projected, +2.2) (27.07)

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official SIDC international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the quicklook Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC ap indices.

This report has been prepared by Jan Alvestad. It is based on analysis of data from whatever sources are available at the time the report is prepared. All time references are to the UTC day. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.